Dead (electronic) speedo and odometer on 1990 RRC

Speedo and odometer on my RR has been dead for some time and I suppose I ought to find out what's wrong.

Suggestions as to how to test the various bits are sought from the font of wisdom, please!

It looks as though getting the transducer off the chassis rail would be a total ordeal so I don't really want to take it off if I can test it in situ - especially if I find that it is functioning.

Also, does anyone know what the o/p of the transducer is so that I can try to reproduce the signal as a means of testing the speedo.

Is there likely to be a simpler fault?

TIA

Richard

Reply to
Richard Savage
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The drive to the sensor... Bad/dirty connectors on the electrical side?

What other errors are showing, or things not working quite right, the speed signal on some vehicles is used for all sorts of things, Aircon/heating settings, radio volume/tonal ballance, suspension firmness ride hight vs speed etc etc. Just showing you how fast your going is incidenta....

The sensor output is probably digital.

For a good intro to automotive electronic deviousness, look at:-

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Take care, much of that stuff is electricaly delicate too, so it won't survive an accidental short to 12V...

Dave B.

Reply to
DaveB

Thanks Dave. Will look at that site.

There are no 'incidentals' in a 1990 RRC! The speed transducer only, as far as I can work out, feeds a little (stepper?) motor in the speedo unit which operates the speedo needle, odometer and trip recorder.

I'm tempted to connect an oscilloscope to the o/p of the transducer and spin the drive with an electric drill. But I was hoping that some kind soul was going to tell me of their frustrating lack of success with that or similar attempts at solving the same problem. I've tolerated the dead speedo for the last 3 MOT tests and used a spare TomTom as a speedo but it's not great. I'd take the transducer off the vehicle for a closer examination only it's fixed by one of the transmission supports which appears to need more serious spannering than I can exert while lying under the vehicle in the snow.

Rgds

Richard

Reply to
Richard Savage

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